Fibrous structures comprising surface softening compositions are known in the art. Silicones and quaternary ammonium compounds have been widely used in the past as surface softening agents within surface softening compositions for various fibrous structures from textiles and fabrics to sanitary tissue products, such as toilet paper, facial tissue, paper towels, and wipes.
Unfortunately, the current surface softening agents have a number of drawbacks which include high cost, a narrow pH formulation window, less than desirable stability and/or softening performance. In an effort to alleviate such drawbacks, new surface softening agents have continued to be developed. Unfortunately, even such newly developed surface softening agents continue to exhibit one or more of the abovementioned drawbacks. Applicants recognized that the aforementioned drawbacks are due to one or more of the following factors: hydrolytic instability of ester linkage which is beta to the quaternary ammonium group in the molecule causes pH intolerance, the high charge density of quaternary ammonium headgroup causes salt intolerance, and excessively high molecular weights of the polymeric softening agents makes them difficult to process and dispose of. Thus what is required are surface softening agents that comprise a material that functions to soften the fibrous structures they are applied to, but does not exhibit the same level of drawbacks as current surface softening agents.
Accordingly, there is a need for surface softening agents that when applied to a surface of a fibrous structure provides the fibrous structure with softness without the drawbacks discussed above, sanitary tissue products comprising such fibrous structures, and methods for making same.